1. Field of the Invention
The present invention relates to an exercise device, and more particularly relates to an exercise device providing ergonomic paths and variable strides.
2. Description of Related Art
Without limiting the disclosed embodiments, a stair stepper, is an exercise device to elevate the heart rate, burn calories and improve cardiovascular endurance.
On a typical stair stepper, a user stands on two platforms supported by a given level of resistance. The user lifts alternating feet, as if walking up a set of stairs, so as to build muscle in legs and gluteus. The stair stepper is also a lower-impact training machine compared to a treadmill, making it useful for those with leg injuries. However, the stair stepper should be used with caution because inadequately activating will place additional stress on the knees.
FIG. 1A and FIG. 1B show two conventional stair steppers. FIG. 1 shows a convention stair stepper with an axis 21 and a pedal 20 coupling with the axis 21 via a rod 22, so that the pedal 20 moves along a path P. FIG. 2 shows another conventional stair stepper with two axis 21 and a pedal 20 coupling with the two axis 21 via two rods 22, so that the pedal 20 moves along a path P. Noticed that the both paths P are an arc with a center pointing away the user, and the paths P are not ergonomic and thus cannot simulate the real stepping, striding, or stair-climbing.
US patent US20120077645 discloses a stair stepper, in which the crank arm exerts force to the linking units, so that the pedal link coupled with the linking units can be moved forward and backward. Each pedal link has a rollable anti-friction member to pivotally couple with the pedal. When the pedal link is moved forward, the rollable anti-friction member drags the pedal climbing forwardly and upwardly along the ramp rod. However, the climbing force of the pedals is unsufficient, and thus the design is not a good solution to simulate stepping, striding, or stair-climbing.
The detail of conventional steppers can also refer to Taiwan patent I458519, entitled “adjustable stepper,” and Taiwan patent I442955, entitled “stepper,” the entire contents of the foregoing applications are incorporated herein for reference.
In addition, conventional steppers typically suffer from a “dead point” problem. The dead point is a point that when a crank and a link of a linking mechanism are operated to be overlapped, it is difficult to further move the crank.